Cell handover method and device

ABSTRACT

Embodiments of the present invention provide a cell handover method and a device. so that the target eNB uses a current serving small node as a user plane serving node after UE is handed over and uses the target eNB as a control plane serving node after the UE is handed over; receiving a handover request acknowledgment sent by the target eNB; and sending offloading configuration information of the current serving small node to the current serving small node, and sending RRC reconfiguration information of the UE to the UE, so that offloading configuration is performed separately by the current serving small node and the UE. This avoids a problem that in a cell handover process, a transmission resource required for transmission increases and a delay is relatively great because the current serving small node forwards a large amount of data to the target eNB.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/884,360, filed on Oct. 15, 2015, which is a continuation ofInternational Application No. PCT/CN2013/074252, filed on Apr. 16, 2013.The afore-mentioned patent applications are hereby incorporated byreference in their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to communicationstechnologies, and in particular, to a cell handover method and a device.

BACKGROUND

As mobile communications technologies develop rapidly, mobile dataservice traffic also increases sharply. To resolve a problem that themobile data service traffic increases sharply, operators propose use ofa small cell for offloading, that is, in a location with a relativelylarge quantity of mobile users, small cells with a relatively smallcoverage area are intensively deployed, so as to support enormousservices generated in this area. An access node of the small cell isreferred to as a small node, where the small node may be a low powernode (LPN, Low Power Node), a femtocell (Femto), a low mobility cell(LoMo), a pico cell (pico), or the like.

The small node is generally deployed in an edge area of a macro basestation. When user equipment (UE, User Equipment) is located in an areacovered synchronously by the macro base station and the small node, anoffloading transmission scheme may be used, that is, control planesignaling of the UE is transmitted in a source eNB (eNB, evolved NodeB), and user plane data is transmitted in the small node. To perform acell handover, the source eNB selects a target eNB for the UE accordingto a measurement result of the UE and radio resource management (RRM,Radio Resource Management) information. To ensure continuity andlossless transmission of a service, the source eNB switches a controlplane and a user plane of the UE to those of the target eNB, andmeanwhile, the LPN forwards, to the target eNB, user plane data of theUE buffered in a buffer.

However, because data stored in a buffer of the small node greatlyincreases user plane data is offloaded to the small cell, when the cellhandover is being performed, a current serving small node needs toforward the data to the target eNB; therefore, a transmission resourcerequired for transmission also increases, and a delay is relativelygreat.

SUMMARY

Embodiments of the present invention provide a cell handover method anda device, so as to avoid a problem that in a cell handover process, atransmission resource required for transmission increases and a delay isrelatively great because a small node forwards a large amount of data toa target eNB.

According to a first aspect, the present invention provides a cellhandover method, including:

sending a handover request to a target eNB eNB, where the handoverrequest includes a context of a current serving small node, a context ofuser equipment UE, and an offloading indication, so that the target eNBuses the current serving small node as a user plane serving node afterthe UE is handed over, and uses the target eNB as a control planeserving node after the UE is handed over;

receiving a handover request acknowledgment sent by the target eNB,where the handover request acknowledgment includes radio resourcecontrol RRC reconfiguration information of the UE and offloadingconfiguration information of the current serving small node, and thehandover request acknowledgment is sent after the target eNB determinesthat the UE can be handed over, that the current serving small node canserve as the user plane serving node after the UE is handed over, andthat the target eNB can serve as the control plane serving node afterthe UE is handed over; and

sending the offloading configuration information of the current servingsmall node to the current serving small node, and sending the RRCreconfiguration information of the UE to the UE, so that offloadingconfiguration is performed separately by the current serving small nodeand the UE.

In a first possible implementation manner of the first aspect, beforethe sending a handover request to a target eNB eNB, the method includes:

determining, according to a measurement report of the UE and radioresource management RRM information, one eNB from a pre-obtained smallnode sharing list as the target eNB to which the UE is to be handedover, where the small node sharing list includes identities IDs ofmultiple eNBs that share the current serving small node; or

determining, according to the measurement report of the UE and the RRMinformation, one eNB as the target eNB to which the UE is to be handedover.

In a second possible implementation manner of the first aspect, thecontext of the current serving small node includes:

an identity of the current serving small node.

According to the second possible implementation manner of the firstaspect, in a third possible implementation manner, the context of thecurrent serving small node further includes:

a use frequency and system information that are of the current servingsmall node, and a security algorithm supported by the current servingsmall node.

According to a second aspect, the present invention provides a cellhandover method, including:

receiving a handover request sent by a source eNB eNB, where thehandover request includes a context of a current serving small node, acontext of user equipment UE, and an offloading indication;

determining, according to the handover request, whether the UE can behanded over, whether the current serving small node can serve as a userplane serving node after the UE is handed over, and whether a target eNBcan serve as a control plane serving node after the UE is handed over,and if the UE can be handed over, the current serving small node canserve as the user plane serving node after the UE is handed over, andthe target eNB can serve as the control plane serving node after the UEis handed over, generating radio resource control RRC reconfigurationinformation of the UE and offloading configuration information of thecurrent serving small node; and

sending, to the source eNB, a handover request acknowledgment thatcarries the RRC reconfiguration information of the UE and the offloadingconfiguration information of the current serving small node, so that thesource eNB sends the RRC reconfiguration information of the UE to the UEand sends the offloading configuration information of the currentserving small node to the current serving small node.

In a first possible implementation manner of the second aspect, afterthe sending, to the source eNB, a handover request acknowledgment thatcarries the RRC reconfiguration information of the UE and the offloadingconfiguration information of the current serving small node, the methodfurther includes:

receiving an uplink synchronization message that is sent by the UE afterthe UE completes offloading configuration according to the RRCreconfiguration information of the UE, and delivering a timing advanceTA and an uplink grant to the UE; and

receiving an offloading configuration success message sent by the UEbased on the TA and the uplink grant.

According to the first possible implementation manner of the secondaspect, in a second possible implementation manner, after the receivingan offloading configuration success message sent by the UE based on theTA and the uplink grant, the method further includes:

sending the UE offloading configuration success indication to thecurrent serving small node, so that the current serving small nodeconfirms that the UE completes the offloading configuration.

According to a third aspect, the present invention provides a cellhandover method, including:

receiving offloading configuration information sent by a source eNB eNB,where the offloading configuration information is sent after the sourceeNB receives a handover request acknowledgment sent by a target eNB towhich user equipment UE is to be handed over, and the offloadingconfiguration information includes configuration information requiredfor establishing a bearer with the target eNB and configurationinformation required for establishing a user plane connection to the UE;

performing offloading configuration according to the offloadingconfiguration information, buffering user plane data of the UE, andrecording a sending status of the user plane data of the UE; and

after confirming that the UE completes the offloading configuration,sending the buffered user plane data of the UE according toconfiguration information obtained after offloading configuration of asmall node and the sending status of the user plane data of the UE.

In a first possible implementation manner of the third aspect, theconfirming that the UE completes the offloading configuration includes:

receiving a UE offloading configuration success indication sent by thetarget eNB; and

confirming, according to the UE offloading configuration successindication, that the UE completes the offloading configuration.

In a second possible implementation manner of the third aspect, theconfirming that the UE completes the offloading configuration includes:

receiving an uplink synchronization message sent by the UE, anddelivering a timing advance TA and an uplink grant to the UE;

receiving an offloading configuration success message sent by the UEbased on the TA and the uplink grant; and

confirming, according to the offloading configuration success message,that the UE completes the offloading configuration.

With reference to the third aspect or either of the possibleimplementation manners of the third aspect, in a third possibleimplementation manner, the buffered user plane data of the UE includesbuffered uplink user plane data and buffered downlink user plane data;and

the sending the buffered user plane data of the UE according toconfiguration information obtained after offloading configuration of asmall node and the sending status of the user plane data of the UEincludes:

sending the buffered downlink user plane data to the UE and the buffereduplink user plane data to the target eNB according to the configurationinformation obtained after the offloading configuration of the smallnode and the sending status of the user plane data of the UE.

According to the third possible implementation manner of the thirdaspect, in a fourth possible implementation manner, the buffereddownlink user plane data includes downlink user plane data from thesource eNB and downlink user plane data from the target eNB; and

the sending the buffered downlink user plane data to the UE according tothe configuration information obtained after the offloadingconfiguration of the small node and the sending status of the user planedata of the UE includes:

sending, to the UE, the downlink user plane data from the source eNBaccording to the configuration information obtained after the offloadingconfiguration of the small node and the sending status of the user planedata of the UE; and

after sending the downlink user plane data from the source eNB iscompleted, sending, to the UE, the downlink user plane data from thetarget eNB according to the configuration information obtained after theoffloading configuration of the small node and the sending status of theuser plane data of the UE.

According to a fourth aspect, the present invention provides an eNB,including:

a sending module, configured to send a handover request to a target eNBeNB, where the handover request includes a context of a current servingsmall node, a context of user equipment UE, and an offloadingindication, so that the target eNB uses the current serving small nodeas a user plane serving node after the UE is handed over, and uses thetarget eNB as a control plane serving node after the UE is handed over;and

a receiving module, configured to receive a handover requestacknowledgment sent by the target eNB, where the handover requestacknowledgment includes radio resource control RRC reconfigurationinformation of the UE and offloading configuration information of thecurrent serving small node, and the handover request acknowledgment issent after the target eNB determines that the UE can be handed over,that the current serving small node can serve as the user plane servingnode after the UE is handed over, and that the target eNB can serve asthe control plane serving node after the UE is handed over; where

the sending module is further configured to: send the offloadingconfiguration information of the current serving small node to thecurrent serving small node, and send the RRC reconfiguration informationof the UE to the UE, so that offloading configuration is performedseparately by the current serving small node and the UE.

In a first possible implementation manner of the fourth aspect, the eNBfurther includes:

a determining module, configured to: determine, according to ameasurement report of the UE and radio resource management RRMinformation, one eNB from a pre-obtained small node sharing list as thetarget eNB to which the UE is to be handed over, where the small nodesharing list includes identities IDs of multiple eNBs that share thecurrent serving small node; or configured to determine, according to themeasurement report of the UE and the RRM information, one eNB as thetarget eNB to which the UE is to be handed over.

In a second possible implementation manner of the fourth aspect, thecontext of the current serving small node includes:

an identity of the current serving small node.

According to the second possible implementation manner of the fourthaspect, in a third possible implementation manner, the context of thecurrent serving small node further includes:

a use frequency and system information that are of the current servingsmall node, and a security algorithm supported by the current servingsmall node.

According to a fifth aspect, the present invention provides an eNB,including:

a receiving module, configured to receive a handover request sent by asource eNB eNB, where the handover request includes a context of acurrent serving small node, a context of user equipment UE, and anoffloading indication;

a judging module, configured to: determine, according to the handoverrequest, whether the UE can be handed over, whether the current servingsmall node can serve as a user plane serving node after the UE is handedover, and whether a target eNB can serve as a control plane serving nodeafter the UE is handed over, and if the UE can be handed over, thecurrent serving small node can serve as the user plane serving nodeafter the UE is handed over, and the target eNB can serve as the controlplane serving node after the UE is handed over, generate radio resourcecontrol RRC reconfiguration information of the UE and offloadingconfiguration information of the current serving small node; and

a sending module, configured to send, to the source eNB, a handoverrequest acknowledgment that carries the RRC reconfiguration informationof the UE and the offloading configuration information of the currentserving small node, so that the source eNB sends the RRC reconfigurationinformation of the UE to the UE and sends the offloading configurationinformation of the current serving small node to the current servingsmall node.

In a first possible implementation manner of the fifth aspect, thereceiving module is further configured to receive an uplinksynchronization message that is sent by the UE after the UE completesoffloading configuration according to the RRC reconfigurationinformation of the UE;

the sending module is further configured to deliver a time advance TAand an uplink grant to the UE; and

the receiving module is further configured to receive an offloadingconfiguration success message sent by the UE based on the TA and theuplink grant.

According to the first possible implementation manner of the fifthaspect, in a second possible implementation manner,

the sending module is further configured to send the UE offloadingconfiguration success indication to the current serving small node, sothat the current serving small node confirms that the UE completes theoffloading configuration.

According to a sixth aspect, the present invention provides a smallnode, including:

a receiving module, configured to receive offloading configurationinformation sent by a source eNB eNB, where the offloading configurationinformation is sent after the source eNB receives a handover requestacknowledgment sent by a target eNB to which user equipment UE is to behanded over, and the offloading configuration information includesconfiguration information required for establishing a bearer with thetarget eNB and configuration information required for establishing auser plane connection to the UE;

a buffering module, configured to: perform offloading configurationaccording to the offloading configuration information, buffer user planedata of the UE, and record a sending status of the user plane data ofthe UE; and

a sending module, configured to: after it is confirmed that the UEcompletes the offloading configuration, send, according to configurationinformation obtained after offloading configuration of the small nodeand the sending status of the user plane data of the UE, the user planedata of the UE buffered by the buffering module.

In a first possible implementation manner of the sixth aspect, thereceiving module is further configured to receive a UE offloadingconfiguration success indication sent by the target eNB; and

the small node further includes: a first confirming module, configuredto confirm, according to the UE offloading configuration successindication, that the UE completes the offloading configuration.

In a second possible implementation manner of the sixth aspect, thereceiving module is further configured to receive an uplinksynchronization message sent by the UE, and the sending module isfurther configured to deliver a timing advance TA and an uplink grant tothe UE;

the receiving module is further configured to receive an offloadingconfiguration success message sent by the UE based on the TA and theuplink grant; and

the small node further includes: a second confirming module, configuredto confirm, according to the offloading configuration success message,that the UE completes the offloading configuration.

With reference to the sixth aspect or either of the possibleimplementation manners of the sixth aspect, in a third possibleimplementation manner, the user plane data of the UE buffered by thebuffering module includes buffered uplink user plane data and buffereddownlink user plane data; and

the sending module is specifically configured to: after it is confirmedthat the UE completes the offloading configuration, according to theconfiguration information obtained after the offloading configuration ofthe small node and the sending status that is of the user plane data ofthe UE and is recorded by the buffering module, send, to the UE, thedownlink user plane data buffered by the buffering module, and send, tothe target eNB, the uplink user plane data buffered by the bufferingmodule.

According to the third possible implementation manner of the sixthaspect, in a fourth possible implementation manner, the downlink userplane data buffered by the buffering module includes downlink user planedata from the source eNB and downlink user plane data from the targeteNB; and

the sending module is specifically configured to: after it is confirmedthat the UE completes the offloading configuration, send, to the UE, thedownlink user plane data from the source eNB according to theconfiguration information obtained after the offloading configuration ofthe small node and the sending status that is of the user plane data ofthe UE and is recorded by the buffering module; and after sending thedownlink user plane data from the source eNB is completed, send, to theUE, the downlink user plane data from the target eNB according to theconfiguration information obtained after the offloading configuration ofthe small node and the sending status that is of the user plane data ofthe UE and is recorded by the buffering module.

According to the cell handover method and the device provided by theembodiments of the present invention, a handover request is sent to atarget eNB, where the handover request includes a context of a currentserving small node, a context of UE, and an offloading indication, sothat the target eNB uses the current serving small node as a user planeserving node after the UE is handed over and uses the target eNB as acontrol plane serving node after the UE is handed over. In this way,transmission of user plane data is always maintained in the currentserving small node, and a control plane is switched from a source eNB tothe target eNB, thereby resolving a problem that in a cell handoverprocess, a transmission resource required for transmission increases anda delay is relatively great because the current serving small nodeforwards a large amount of data to the target eNB.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showsome embodiments of the present invention, and a person of ordinaryskill in the art may still derive other drawings from these accompanyingdrawings without creative efforts.

FIG. 1 is a flowchart of Embodiment 1 of a cell handover methodaccording to the present invention;

FIG. 2 is a flowchart of Embodiment 2 of a cell handover methodaccording to the present invention;

FIG. 3 is a flowchart of Embodiment 3 of a cell handover methodaccording to the present invention;

FIG. 4 is a flowchart of Embodiment 4 of a cell handover methodaccording to the present invention;

FIG. 5 is a flowchart of Embodiment 5 of a cell handover methodaccording to the present invention;

FIG. 6 is a signaling flowchart of an embodiment of a cell handovermethod according to the present invention;

FIG. 7 is a schematic structural diagram of Embodiment 1 of an eNBaccording to the present invention;

FIG. 8 is a schematic structural diagram of Embodiment 2 of an eNBaccording to the present invention;

FIG. 9 is a schematic structural diagram of Embodiment 1 of a small nodeaccording to the present invention;

FIG. 10 is a schematic structural diagram of Embodiment 3 of an eNBaccording to the present invention;

FIG. 11 is a schematic structural diagram of Embodiment 4 of an eNBaccording to the present invention; and

FIG. 12 is a schematic structural diagram of Embodiment 2 of a smallnode according to the present invention.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of theembodiments of the present invention clearer, the following clearlydescribes the technical solutions in the embodiments of the presentinvention with reference to the accompanying drawings in the embodimentsof the present invention. Apparently, the described embodiments are somebut not all of the embodiments of the present invention. All otherembodiments obtained by a person of ordinary skill in the art based onthe embodiments of the present invention without creative efforts shallfall within the protection scope of the present invention.

Technologies described in this specification may be applied to variouscommunications systems, for example, current 2G and 3G communicationssystems and a next-generation communications system, for example, aGlobal System for Mobile Communications (GSM, Global System for Mobilecommunications), a Code Division Multiple Access (CDMA, Code DivisionMultiple Access) system, a Time Division Multiple Access (TDMA, TimeDivision Multiple Access) system, a Wideband Code Division MultipleAccess (WCDMA, Wideband Code Division Multiple Access) system, aFrequency Division Multiple Access (FDMA, Frequency Division MultipleAccess) system, an Orthogonal Frequency-Division Multiple Access (OFDMA,Orthogonal Frequency-Division Multiple Access) system, a single-carrierFDMA (SC-FDMA) system, a General Packet Radio Service (GPRS, GeneralPacket Radio Service) system, a Long Term Evolution (LTE, Long TermEvolution) system, and other communications systems.

User equipment involved in this application may be a wireless terminalor a wired terminal. The wireless terminal may refer to a device thatprovides a user with voice and/or data connectivity, a handheld devicewith a radio connection function, or another processing device connectedto a radio modem. The wireless terminal may communicate with one or morecore networks through a radio access network (such as RAN, Radio AccessNetwork). The wireless terminal may be a mobile terminal, such as amobile phone (also referred to as a “cellular” phone) and a computerwith a mobile terminal, for example, may be a portable, pocket-sized,handheld, computer built-in, or in-vehicle mobile apparatus, whichexchanges voice and/or data with the radio access network. For example,it may be a device such as a personal communications service (PCS,Personal Communication Service) phone, a cordless telephone set, aSession Initiation Protocol (SIP) phone, a wireless local loop (WLL,Wireless Local Loop) station, or a personal digital assistant (PDA,Personal Digital Assistant). The wireless terminal may also be referredto as a system, a subscriber unit (Subscriber Unit), a subscriberstation (Subscriber Station), a mobile station (Mobile Station), amobile terminal (Mobile), a remote station (Remote Station), an accesspoint (Access Point), a remote terminal (Remote Terminal), an accessterminal (Access Terminal), a user terminal (User Terminal), a useragent (User Agent), a user device (User Device), or user equipment (UserEquipment).

A base station involved in this application is a generalized basestation, includes functions of radio resource management and datascheduling, may include a radio network controller (Radio NetworkController, RNC), and may further include a device in communication witha wireless terminal via one or more sectors at an air interface in anaccess network. The base station may be configured to mutually convert areceived over-the-air frame and an IP packet and serve as a routerbetween the wireless terminal and a rest portion of the access network,where the rest portion of the access network may include an Internetprotocol (IP) network. The base station may also coordinate attributemanagement of the air interface. For example, the base station may be abase station (BTS, Base Transceiver Station) in GSM or the CDMA, mayalso be a base station (NodeB) in WCDMA, and may further be an evolvedNodeB (NodeB, eNB, or e-NodeB, evolved Node B) in the LTE, which is notlimited in the this application.

In embodiments of the present invention, an interface between an eNB andUE is defined as an interface Uu, an interface between a small node andthe UE as an interface Uu′, and an interface between the eNB and thesmall node as an interface X3. A cell handover method of the presentinvention may be applied to a scenario in which the UE is located in anarea covered synchronously by a macro eNB and the small node. Thesequence numbers of the following embodiments of the present inventionare merely for description, and do not imply the preference among theembodiments.

FIG. 1 is a flowchart of Embodiment 1 of a cell handover methodaccording to the present invention. As shown in FIG. 1, the cellhandover method provided in this embodiment is executed by a source eNB,and the cell handover method of this embodiment may include:

S101. Send a handover request to a target eNB eNB, where the handoverrequest includes a context of a current serving small node, a context ofuser equipment UE, and an offloading indication, so that the target eNBuses the current serving small node as a user plane serving node afterthe UE is handed over, and uses the target eNB as a control planeserving node after the UE is handed over.

Specifically, the current serving small node may be an LPN, a Femto, aLoMo, a pico or the like. The current serving small node refers to asmall node that currently provides a user plane service for the UE. Thecurrent serving small node may be a small node located in an areacovered by multiple macro eNBs.

Further, the context of the current serving small node may include anidentity of the current serving small node, may further include a usefrequency and system information that are of the current serving smallnode and a security algorithm supported by the current serving smallnode, and may also include, in the handover request, an informationelement (Information Element, IE for short) that is used to uniquelydefine, on an interface X3, a serial number of the UE.

It should be noted that when a signal quality of a cell does not meet arequirement, the UE sends a corresponding measurement report to thesource eNB, and after receiving the measurement report of the UE and RRMinformation, the source eNB determines one eNB as the target eNB towhich the UE is to be handed over. Optionally, the source eNB maydetermine one eNB from a pre-obtained small node sharing list as thetarget eNB to which the UE is to be handed over, where the small nodesharing list includes identities (ID, Identity) of multiple eNBs thatshare a current serving small node. The small node sharing list may becreated by the current serving small node or by operation,administration and maintenance OAM (operation, administration andmaintenance). The current serving small node stores the small nodesharing list and transmits, by using the interface X3, the small nodesharing list to each eNB that shares the current serving small node.Further, when a change occurs in the small node sharing list, that is, achange occurs in eNBs that share the current serving small node, thecurrent serving small node may further update the small node sharinglist and transmit the small node sharing list to each eNB that currentlyshares the resource of the current serving small node.

Optionally, the source eNB may also determine, according to themeasurement report of the UE and the RRM information, one eNB as thetarget eNB to which the UE is to be handed over, so that the target eNBuses the current serving small node as the user plane serving node afterthe UE is handed over and uses the target eNB as the control planeserving node after the UE is handed over.

S102. Receive a handover request acknowledgment sent by the target eNB,where the handover request acknowledgment includes radio resourcecontrol RRC reconfiguration information of the UE and offloadingconfiguration information of the current serving small node, and thehandover request acknowledgment is sent after the target eNB determinesthat the UE can be handed over, that the current serving small node canserve as the user plane serving node after the UE is handed over, andthat the target eNB can serve as the control plane serving node afterthe UE is handed over.

Specifically, the RRC reconfiguration information of the UE may includeUE side configuration information related to establishment of a userplane connection to the current serving small node and configurationinformation required for establishing a control plane connection to thetarget eNB. The UE side configuration information related to theestablishment of the user plane connection to the current serving smallnode may include a physical cell identifier (PCI, Physical CellIdentifier) of the current serving small node, system information, afrequency, a data radio bearer (DRB, Data Radio Bearer), configurationsof a transmission channel and a physical channel, and an access preambleexclusive for the current serving small node, where the systeminformation, the frequency, the data radio bearer, and theconfigurations of the transmission channel and the physical channel areused by the current serving small node. The configuration informationrequired for establishing the control plane connection to the target eNBmay include an access preamble exclusive for the target eNB. Theoffloading configuration information of the current serving small nodemay include configuration information required for establishing a userplane connection to the UE and configuration information required forestablishing a bearer with the target eNB. Configuration informationrequired for establishing the user plane connection to the UE mayinclude configurations of a logical channel, a transmission channel, anda physical channel, a new security algorithm identifier, and a new key.The configuration information required for establishing the bearer withthe target eNB may include configurations of a logical channel, atransmission channel, and a physical channel, a new security algorithmidentifier, and a new key that are related to the interface X3.

S103. Send the offloading configuration information of the currentserving small node to the current serving small node, and send the RRCreconfiguration information of the UE to the UE, so that offloadingconfiguration is performed separately by the current serving small nodeand the UE.

Specifically, after receiving the handover request acknowledgment, thesource eNB sends the offloading configuration information of the currentserving small node to the current serving small node, and sends the RRCreconfiguration information of the UE to the UE at the same time, sothat the offloading configuration is performed separately by the currentserving small node and the UE.

According to the cell handover method provided in this embodiment, ahandover request is sent to a target eNB, where the handover requestincludes a context of a current serving small node, a context of UE, andan offloading indication, so that the target eNB uses the currentserving small node as a user plane serving node after the UE is handedover and uses the target eNB as a control plane serving node after theUE is handed over. In this way, transmission of user plane data isalways maintained in the current serving small node, and a control planeis switched from a source eNB to the target eNB, thereby resolving aproblem that in a cell handover process, a transmission resourcerequired for transmission increases and a delay is relatively greatbecause the current serving small node forwards a large amount of datato the target eNB.

FIG. 2 is a flowchart of Embodiment 2 of a cell handover methodaccording to the present invention. As shown in FIG. 2, the cellhandover method provided in this embodiment is executed by a source eNB,and on the basis of the foregoing embodiment, after step S103, the cellhandover method of this embodiment may also include:

S204. Receive an end mark sent by a serving gateway (S-GW, ServingGateway).

Generally, after completing the offloading configuration, the UE sendsan offloading configuration success message to the target eNB; thetarget eNB sends a path switch request to a mobility management entity(MME, Mobility Management Entity) so as to indicate that a serving cellof the UE has changed; the MME sends a bearer modifying request to theS-GW, and the S-GW switches a sending path of downlink data to thetarget eNB and sends several end marks to the source eNB.

S205. Forward the end mark to the current serving small node, so thatthe current serving small node releases, according to the end mark, aresource that is established with the source eNB and that is related tothe UE.

Specifically, after receiving the end mark and confirming that thesource eNB does not have a resource to deliver, the current servingsmall node releases the resource that is established with the source eNBand that is related to the UE, for example, an X3 interface resource.

S206. Receive a context release request sent by the target eNB, wherethe context release request is sent after the target eNB confirms that adownlink path switch of the LTE by the S-GW is completed.

Generally, after receiving the offloading configuration success messageof the UE, the target eNB sends the path switch request to the MME. Whenthe target eNB receives a path switch request acknowledgment sent by theMME, the target eNB sends the context release request to the source eNB.

S207. Release the context related to the UE according to the contextrelease request.

Optionally, when receiving the end mark forwarded in S205, the currentserving small node may not release the resource that is establishedbetween the current serving small node and the source eNB and that isrelated to the UE either; instead, after S207, and after the source eNBreceives the context release request sent by the target eNB and releasesthe context related to the UE, the source eNB sends a resource releaserequest to the current serving small node, so that the current servingsmall node releases the resource that is established with the source eNBand that is related to the UE.

According to the cell handover method provided in this embodiment, onthe basis of Embodiment 1, a handover request acknowledgment sent by atarget eNB to a source eNB carries UE side configuration informationrelated to establishment of a user plane connection to a current servingsmall node, so that offloading configuration is performed separately byUE and the current serving small node; after the UE and the currentserving small node complete the offloading configuration, the currentserving small node releases a resource that is established between thecurrent serving small node and the source eNB and that is related to theUE, and the source eNB releases a context related to the UE, therebysaving a resource.

FIG. 3 is a flowchart of Embodiment 3 of a cell handover methodaccording to the present invention. As shown in FIG. 3, the cellhandover method provided in this embodiment is executed by a target eNB,and the cell handover method of this embodiment may include:

S301. Receive a handover request sent by a source eNB eNB, where thehandover request includes a context of a current serving small node, acontext of user equipment UE, and an offloading indication.

Specifically, the handover request may further include a use frequencyand system information that are of the current serving small node and asecurity algorithm supported by the current serving small node. Thehandover request may further include an information element that is usedto uniquely define, on interface X3, a serial number of the UE.

S302. Determine, according to the handover request, whether the UE canbe handed over, whether the current serving small node can serve as auser plane serving node after the UE is handed over, and whether atarget eNB can serve as a control plane serving node after the UE ishanded over, and if the UE can be handed over, the current serving smallnode can serve as the user plane serving node after the UE is handedover, and the target eNB can serve as the control plane serving nodeafter the UE is handed over, generate RRC reconfiguration information ofthe UE and offloading configuration information of the current servingsmall node.

Specifically, the RRC reconfiguration information of the UE and theoffloading configuration information of the current serving small nodeare generated only when it is determined that the UE can be handed over,that the current serving small node can serve as the user plane servingnode after the UE is handed over, and that the target eNB can serve asthe control plane serving node after the UE is handed over. If it isdetermined that the UE cannot be handed over, a reason why a handovercannot be completed is indicated in handover request acknowledgmentinformation; if it is determined that the UE can be handed over, but thecurrent serving small node cannot serve as the user plane serving nodeafter the UE is handed over, the source eNB is instruct to switch acontrol plane and a user plane of the UE to those of the target eNB, andforward user plane data buffered by the current serving small node.

S303. Send, to the source eNB, a handover request acknowledgment thatcarries the RRC reconfiguration information of the UE and the offloadingconfiguration information of the current serving small node, so that thesource eNB sends the RRC reconfiguration information of the UE to the UEand sends the offloading configuration information of the currentserving small node to the current serving small node.

Specifically, the RRC reconfiguration information of the UE may includeUE side configuration information related to establishment of a userplane connection to the current serving small node and configurationinformation required for establishing a control plane connection to thetarget eNB. The UE side configuration information related to theestablishment of the user plane connection to the current serving smallnode may include a PCI of the current serving small node, systeminformation, a frequency, a DRB, configurations of a transmissionchannel and a physical channel, and an access preamble exclusive for thecurrent serving small node, where the system information, the frequency,the DRB, and the configurations of the transmission channel and thephysical channel are used by the current serving small node. Theconfiguration information required for establishing the control planeconnection to the target eNB may include an access preamble exclusivefor the target eNB. The offloading configuration information of thecurrent serving small node may include configuration informationrequired for establishing a user plane connection to the UE andconfiguration information required for establishing a bearer with thetarget eNB. The configuration information required for establishing theuser plane connection to the UE may include configurations of a logicalchannel, a transmission channel, and a physical channel, a new securityalgorithm identifier, and a new key that are related to an interfaceUu′. The configuration information required for establishing the bearerwith the target eNB may include configurations of a logical channel, atransmission channel, and a physical channel, a new security algorithmidentifier, and a new key that are related to the interface X3.

According to the cell handover method provided in this embodiment. Afterreceiving a handover request, a target eNB determines whether a handovercan be performed, whether a current serving small node can serve as auser plane serving node after the UE is handed over, and whether thetarget eNB can serve as a control plane serving node after the UE ishanded over, and if a handover can be performed, the current servingsmall node can serve as the user plane serving node after the UE ishanded over, and the target eNB can serve as the control plane servingnode after the UE is handed over, generates RRC reconfigurationinformation of the UE and offloading configuration information of thecurrent serving small node, and sends, to a source eNB, a handoverrequest acknowledgment that carries the RRC reconfiguration informationof the UE and the offloading configuration information of the currentserving small node, so as to perform a cell handover. In this way,transmission of user plane data is always maintained in the currentserving small node, and a control plane is switched from the source eNBto the target eNB, thereby resolving a problem that in a cell handoverprocess, a transmission resource required for transmission increases anda delay is relatively great because the current serving small nodeforwards a large amount of data to the target eNB.

FIG. 4 is a flowchart of Embodiment 4 of a cell handover methodaccording to the present invention. As shown in FIG. 4, the cellhandover method provided in this embodiment is executed by a target eNB,and on the basis of the foregoing embodiment, after step S303, the cellhandover method of this embodiment may include:

S404. Receive an uplink synchronization message sent by the UE after theUE completes the offloading configuration according to the RRCreconfiguration information of the UE, and deliver a timing advance TAand an uplink grant to the UE.

Specifically, after completing the offloading configuration, the UE maysend the uplink synchronization message to the target eNB by using theaccess preamble that is in the RRC reconfiguration information and thatis exclusive for the target eNB.

S405. Receive an offloading configuration success message sent by the UEbased on the TA and the uplink grant.

S406. Send a UE offloading configuration success indication to thecurrent serving small node, so that the current serving small nodeconfirms that the UE completes the offloading configuration.

It should be noted that in this embodiment of the present invention,there are two implementation scenarios. The first scenario is that aftercompleting the offloading configuration, the UE initiates uplinksynchronization only to the target eNB; and the second scenario is thatafter completing the offloading configuration, the UE initiates uplinksynchronization to both the target eNB and the current serving smallnode. In the first scenario, the target eNB executes step S406 afterstep S405. In the second scenario, the UE sends the offloadingconfiguration success message separately to the target eNB and thecurrent serving small node after the uplink synchronization iscompleted. Correspondingly, the target eNB does not need to execute stepS406.

Specifically, after the target eNB sends the UE offloading configurationsuccess indication to the current serving small node, or after thetarget eNB and the current serving small node both receive theoffloading configuration success message that is sent by the UE afterthe uplink synchronization is completed, a transmission path of uplinkuser plane data of the UE is switched to the target eNB.

The target eNB starts to receive the uplink user plane data of the UEsent by the current serving small node, and forwards the uplink userplane data of the UE to an EPC (EPC, Evolved Packet Core).

S407. Send a path switch request to an MME to indicate that a servingcell of the UE has changed, so that the MME sends a bearer modifyingrequest to an S-GW.

S408. Receive a path switch request acknowledgment sent by the MME,where the path switch request acknowledgment is sent to the target eNBby the MME after receiving a bearer modifying response of the S-GW.

Generally, after receiving the path switch request sent by the targeteNB, the MME sends the bearer modifying request to the S-GW; aftercompleting a switch of a transmission path of downlink data, the S-GWsends the bearer modifying response to the MME; after receiving thebearer modifying response, the MME sends the path switch requestacknowledgment to the target eNB.

S409. Send a context release request to the source eNB, so that thesource eNB releases the context related to the UE.

According to the cell handover method provided in this embodiment, onthe basis of the foregoing embodiment, a handover request acknowledgmentsent by a target eNB to a source eNB carries UE side configurationinformation related to establishment of a user plane connection to acurrent serving small node, so that offloading configuration isseparately performed by UE the current serving small node. After the UEand the current serving small node complete the offloadingconfiguration, the target eNB sends a context release request, so thatthe source eNB releases a context related to the UE. In this way,transmission of user plane data is always maintained in the currentserving small node, and a control plane is switched from the source eNBto the target eNB, thereby resolving a problem that in a cell handoverprocess, a transmission resource required for transmission increases anda delay is relatively great because the current serving small nodeforwards a large amount of data to the target eNB.

FIG. 5 is a flowchart of Embodiment 5 of a cell handover methodaccording to the present invention. As shown in FIG. 5, the cellhandover method provided in this embodiment is executed by a currentserving small node, and the cell handover method of this embodiment mayinclude:

S501. Receive offloading configuration information sent by a source eNBeNB, where the offloading configuration information is sent after thesource eNB receives a handover request acknowledgment sent by a targeteNB to which user equipment UE is to be handed over, and the offloadingconfiguration information includes configuration information requiredfor establishing a bearer with the target eNB and configurationinformation required for establishing a user plane connection to the UE.

Specifically, the current serving small node is a small node thatcurrently provides a service for the UE.

S502. Perform offloading configuration according to the offloadingconfiguration information, buffer user plane data of the UE, and recorda sending status of the user plane data of the UE.

Specifically, according to the received offloading configurationinformation, the current serving small node performs correspondingoffloading configuration, and stores the sending status of the userplane data of the UE, that is, SN Status information. The SN Statusinformation includes transmission statuses of an uplink packet dataconvergence protocol serial number (PDCP SN, Packet Data ConvergenceProtocol Serial Number) receiver and a downlink PDCH SN transmitter, soas to ensure lossless transmission in a handover process, and meanwhile,buffer the user plane data of the UE. The user plane data includes PDCPSDUs and data to which an SN is not allocated, where the PDCP SDU aredata to which an SN has already been allocated.

S503. After it is confirmed that the UE completes the offloadingconfiguration, send the buffered user plane data of the UE according toconfiguration information of the current serving small node obtainedafter its own offloading configuration and the sending status of theuser plane data of the UE.

Specifically, the buffered user plane data of the UE may includebuffered uplink user plane data and buffered downlink user plane data,where the buffered downlink user plane data may include downlink userplane data from the source eNB and downlink user plane data from thetarget eNB.

Further, according to the configuration information of the currentserving small node obtained after its own offloading configuration andthe sending status of the user plane data of the UE, the current servingsmall node sends the buffered downlink user plane data to the UE, andsends the buffered uplink user plane data to the target eNB.

When sending the buffered downlink user plane data, the current servingsmall node first sends, to the UE, the downlink user plane data from thesource eNB, and after sending the downlink user plane data from thesource eNB is completed, sends, to the UE, the downlink user plane datafrom the target eNB according to the configuration information of thecurrent serving small node obtained after its own offloadingconfiguration and the sending status of the user plane data of the UE.

According to the cell handover method provided in this embodiment, asmall node receives offloading configuration information sent by asource eNB to perform offloading configuration, buffers user plane dataof UE, and after it is confirmed that the UE completes the offloadingconfiguration, sends the buffered user plane data of the UE according toconfiguration information obtained after offloading configuration of thesmall node and a recorded sending status of the user plane data of theUE, so that transmission of user plane data is always maintained in thecurrent serving small node, and a control plane is switched from asource eNB to the target eNB, thereby resolving a problem that in a cellhandover process, a transmission resource required for transmissionincreases and a delay is relatively great because a current servingsmall node forwards a large amount of data to the target eNB.

FIG. 6 is a signaling flowchart of an embodiment of a cell handovermethod. As shown in FIG. 6, the cell handover method provided in thisembodiment includes:

S601. A source eNB sends a handover request to a target eNB.

The source eNB determines, according to a measurement report of UE andRRM information one eNB from a pre-obtained small node sharing list as atarget eNB to which the UE is to be handed over, and sends the handoverrequest to the target eNB, where the handover request includes a contextof a current serving small node, a context of the UE, and an offloadingindication, so that the target eNB uses the current serving small nodeas a user plane serving node after the UE is handed over, and uses thetarget eNB as a control plane serving node after the UE is handed over.

S602. The target eNB determines whether a handover can be performed.

After receiving the handover request sent by the source eNB, the targeteNB determines whether a handover can be performed, whether the currentserving small node can serve as the user plane serving node after the UEis handed over, and whether the target eNB can serve as the controlplane serving node after the UE is handed over, and if a handover can beperformed, the current serving small node can serve as the user planeserving node after the UE is handed over, and the target eNB can serveas the control plane serving node after the UE is handed over, generatesRRC reconfiguration information of the UE and offloading configurationinformation of the current serving small node.

S603. The target eNB sends a handover request acknowledgment to thesource eNB.

The target eNB includes the generated RRC reconfiguration information ofthe UE and offloading configuration information of the current servingsmall node in the handover request acknowledgment sent to the sourceeNB, so that the source eNB sends the RRC reconfiguration information ofthe UE to the UE, and sends the offloading configuration information ofthe current serving small node to the current serving small node.

S604. The source eNB sends the offloading configuration information tothe current serving small node.

The offloading configuration information sent by the source eNB to thesmall node may include configuration information required forestablishing a user plane connection to the UE and configurationinformation required for establishing a bearer with the target eNB, sothat the small node performs offloading configuration.

S605. The source eNB sends the RRC reconfiguration information to theUE.

The RRC reconfiguration information sent by the source eNB to the UE mayinclude UE side configuration information related to establishment of auser plane connection to the current serving small node andconfiguration information required for establishing a control planeconnection to the target eNB, so that the UE performs offloadingconfiguration.

S604 and S605 may be executed at the same time.

S606. After receiving the offloading configuration information, thesmall node performs offloading configuration, and buffers user planedata.

The current serving small node performs corresponding offloadingconfiguration according to the received offloading configurationinformation, and meanwhile, buffers the user plane data of the UE, andstores PDCP SN status information. The PDCP SN status informationincludes transmission statuses of an uplink PDCP SN receiver and adownlink PDCH SN transmitter, so as to ensure lossless transmission in ahandover process.

S607. After completing the offloading configuration, the UE sends anuplink synchronization message to the target eNB.

After completing the offloading configuration, the UE sends the uplinksynchronization message to the target eNB by using an access preambleinformation that is in the RRC reconfiguration information and that isexclusive for the target eNB.

S608. The target eNB sends a TA and an uplink grant to the UE.

After receiving the uplink synchronization message sent by the UE, thetarget eNB sends the TA and the uplink grant to the UE.

S609. The UE sends an offloading configuration success message to thetarget eNB.

The UE sends, based on the TA and the uplink grant, the offloadingconfiguration success message to the target eNB.

S610. The target eNB sends a UE offloading configuration successindication to the small node.

So far, a control plane of the UE is switched from the source eNB to thetarget eNB, whereas transmission of the user plane data is stillmaintained in the small node.

S611. The target eNB sends a path switch request to an MME.

The target eNB sends the path switch request to the MME, so as toindicate that a serving cell of the UE has changed.

S612. The MME sends a bearer modifying request to an S-GW.

After receiving the path switch request sent by the target eNB, the MMEsends the bearer modifying request to the S-GW.

S613. The S-GW sends a bearer modifying response to the MME.

After receiving the bearer modifying request sent by the MME, the S-GWswitches a sending path of downlink data to the target eNB.

S614. The MME sends a path switch request acknowledgment to the targeteNB.

After receiving the bearer modifying response sent by the S-GW, the MMEsends the path switch request acknowledgment to the target eNB.

S615. The target eNB sends a context release request to the source eNB.

After receiving the context release request, the source eNB releases thecontext related to the UE.

A difference between another scenario and that of FIG. 6 lies in that,the UE initiates uplink synchronization to the current serving smallnode when executing S607˜S609, and sends the offloading configurationsuccess message to the current serving small node. Correspondingly,after S609, the target eNB does not need to execute S610, but directlyexecutes S611.

According to the cell handover method provided in this embodiment, oneeNB from a pre-obtained small node sharing list as a target eNB to whichUE is to be handed over and sends a handover request to the target eNB,so that the target eNB uses the current serving small node as a userplane serving node after the UE is handed over and uses the target eNBas a control plane serving node after the UE is handed over. In thisway, transmission of user plane data is always maintained in the currentserving small node, and a control plane is switched from the source eNBto the target eNB, thereby resolving a problem that in a cell handoverprocess, a transmission resource required for transmission increases anda delay is relatively great because the current serving small nodeforwards a large amount of data to the target eNB.

FIG. 7 is a schematic structural diagram of Embodiment 1 of an eNBaccording to the present invention. As shown in FIG. 7, the eNB providedin this embodiment may include:

a sending module 11, configured to send a handover request to a targeteNB, where the handover request includes a context of a current servingsmall node, a context of UE, and an offloading indication, so that thetarget eNB uses the current serving small node as a user plane servingnode after the UE is handed over, and uses the target eNB as a controlplane serving node after the UE is handed over; and

a receiving module 12, configured to receive a handover requestacknowledgment sent by the target eNB, where the handover requestacknowledgment includes radio resource control RRC reconfigurationinformation of the UE and offloading configuration information of thecurrent serving small node, and the handover request acknowledgment issent after the target eNB determines that the UE can be handed over,that the current serving small node can serve as the user plane servingnode after the UE is handed over, and that the target eNB can serve asthe control plane serving node after the UE is handed over; where

the sending module 11 is further configured to: send the offloadingconfiguration information of the current serving small node to thecurrent serving small node, and send the RRC reconfiguration informationof the UE to the UE, so that offloading configuration is performedseparately by the current serving small node and the UE.

Optionally, the eNB further includes: a determining module, configuredto determine, according to a measurement report of the UE and RRMinformation, one eNB from a pre-obtained small node sharing list as thetarget eNB to which the UE is to be handed over, where the small nodesharing list includes IDs of multiple eNBs that share the currentserving small node; or configured to determine, according to themeasurement report of the UE and the RRM information, one eNB as thetarget eNB to which the UE is to be handed over.

Further, the context of the current serving small node includes anidentity of the current serving small node.

Optionally, the context of the current serving small node furtherincludes:

a use frequency and system information that are of the current servingsmall node, and a security algorithm supported by the current servingsmall node.

The eNB in this embodiment may be configured to execute a technicalsolution in the method embodiment shown in FIG. 1 or FIG. 2, and animplementation principle and a technical effect thereof are similar andare not described herein again.

FIG. 8 is a schematic structural diagram of Embodiment 2 of an eNBaccording to the present invention. As shown in FIG. 8, the eNB providedin this embodiment may include:

a receiving module 21, configured to receive a handover request sent bya source eNB, where the handover request includes a context of a currentserving small node, a context of UE, and an offloading indication;

a judging module 22, configured to: determine, according to the handoverrequest, whether the UE can be handed over, whether the current servingsmall node can serve as a user plane serving node after the UE is handedover, and whether the target eNB can serve as a control plane servingnode after the UE is handed over, and if the UE can be handed over, thecurrent serving small node can serve as the user plane serving nodeafter the UE is handed over, and the target eNB can serve as the controlplane serving node after the UE is handed over, generate RRCreconfiguration information of the UE and offloading configurationinformation of the current serving small node; and

a sending module 23, configured to send, to the source eNB, a handoverrequest acknowledgment that carries the RRC reconfiguration informationof the UE and the offloading configuration information of the currentserving small node, so that the source eNB sends the RRC reconfigurationinformation of the UE to the UE and sends the offloading configurationinformation of the current serving small node to the current servingsmall node.

Further, the receiving module 21 is further configured to receive anuplink synchronization message sent by the UE after the UE completes theoffloading configuration according to the RRC reconfigurationinformation of the UE; the sending module 23 is further configured todeliver a timing advance TA and an uplink grant to the UE; the receivingmodule 21 is further configured to receive an offloading configurationsuccess message that is sent by the UE based on the TA and the uplinkgrant.

Further, the sending module 23 is further configured to send a UEoffloading configuration success indication to the current serving smallnode, so that the current serving small node confirms that the UEcompletes the offloading configuration.

The eNB in this embodiment may be configured to execute a technicalsolution in the foregoing method embodiment shown in FIG. 3 or FIG. 4,and an implementation principle and a technical effect thereof aresimilar and are not described herein again.

FIG. 9 is a schematic structural diagram of Embodiment 1 of a small nodeaccording to the present invention. As shown in FIG. 9, the small nodeprovided in this embodiment may include:

a receiving module 31, configured to receive offloading configurationinformation sent by a source eNB, where the offloading configurationinformation is sent after the source eNB receives a handover requestacknowledgment sent by a target eNB to which UE is to be handed over,and the offloading configuration information includes configurationinformation required for establishing a bearer with the target eNB andconfiguration information required for establishing a user planeconnection to the UE;

a buffering module 32, configured to: perform offloading configurationaccording to the offloading configuration information, buffer user planedata of the UE, and record a sending status of the user plane data ofthe UE; and

a sending module 33, configured to: after it is confirmed that the UEcompletes the offloading configuration, send, according to configurationinformation obtained after offloading configuration of the small nodeand the sending status of the user plane data of the UE, the user planedata of the UE buffered by the buffering module 32.

Optionally, the receiving module 31 is further configured to receive aUE offloading configuration success indication sent by the target eNB;correspondingly, the small node further includes: a first confirmingmodule, configured to confirm, according to the UE offloadingconfiguration success indication, that the UE completes the offloadingconfiguration.

Optionally, the receiving module 31 is further configured to receive anuplink synchronization message sent by the UE, and the sending module 33is further configured to deliver a timing advance TA and an uplink grantto the UE.

The receiving module 31 is further configured to receive an offloadingconfiguration success message sent by the UE based on the TA and theuplink grant.

Correspondingly, the small node further includes: a second confirmingmodule, configured to confirm, according to the offloading configurationsuccess message, that the UE completes the offloading configuration.

Further, the user plane data of the UE buffered by the buffering module32 includes buffered uplink user plane data and buffered downlink userplane data.

The sending module 33 is specifically configured to: after it isconfirmed that the UE completes the offloading configuration, accordingto the configuration information obtained after the offloadingconfiguration of the small node and the sending status that is of theuser plane data of the UE and is recorded by the buffering module 32,send, to the UE, the downlink user plane data buffered by the bufferingmodule 32, and send, to the target eNB, the uplink user plane databuffered by the buffering module 32.

Further, the downlink user plane data buffered by the buffering module32 includes downlink user plane data from the source eNB and downlinkuser plane data from the target eNB.

The sending module 33 is specifically configured to: after it isconfirmed that the UE completes the offloading configuration, send, tothe UE, the downlink user plane data from the source eNB according tothe configuration information obtained after the offloadingconfiguration of the small node and the sending status that is of theuser plane data of the UE and is recorded by the buffering module 32;and after sending the downlink user plane data from the source eNB iscompleted, send, to the UE, the downlink user plane data from the targeteNB according to the configuration information obtained after theoffloading configuration of the small node and the sending status thatis of the user plane data of the UE and is recorded by the bufferingmodule 32.

The small node in this embodiment may be configured to execute atechnical solution in the foregoing method embodiment shown in FIG. 5,and an implementation principle and a technical effect thereof aresimilar and are not described herein again.

FIG. 10 is a schematic structural diagram of Embodiment 3 of an eNBaccording to the present invention. As shown in FIG. 10, the eNBprovided in this embodiment may include: a transmitter 41 and a receiver42.

The transmitter 41 is configured to send a handover request to a targeteNB eNB, where the handover request includes a context of a currentserving small node, a context of user equipment UE, and an offloadingindication, so that the target eNB uses the current serving small nodeas a user plane serving node after the UE is handed over, and uses thetarget eNB as a control plane serving node after the UE is handed over.

The receiver 42 is configured to receive a handover requestacknowledgment sent by the target eNB, where the handover requestacknowledgment includes radio resource control RRC reconfigurationinformation of the UE and offloading configuration information of thecurrent serving small node, and the handover request acknowledgment issent after the target eNB determines that the UE can be handed over,that the current serving small node can serve as the user plane servingnode after the UE is handed over, and that the target eNB can serve asthe control plane serving node after the UE is handed over.

The foregoing transmitter 41 is further configured to: send theoffloading configuration information of the current serving small nodeto the current serving small node, and send the RRC reconfigurationinformation of the UE to the UE, so that offloading configuration isperformed separately by the current serving small node and the UE.

Further, a processor is further configured to determine, according to ameasurement report of the UE and RRM information one eNB from apre-obtained small node sharing list as the target eNB to which the UEis to be handed over, where the small node sharing list includes IDs ofmultiple eNBs that share the current serving small node; or configuredto determine, according to the measurement report of the UE and the RRMinformation, one eNB as the target eNB to which the UE is to be handedover.

Further, the context of the current serving small node includes anidentity of the current serving small node.

Optionally, the context of the current serving small node furtherincludes:

a use frequency and system information that are of the current servingsmall node, and a security algorithm supported by the current servingsmall node.

The eNB in this embodiment may be configured to execute a technicalsolution in the foregoing method embodiment shown in FIG. 1 or FIG. 2,and an implementation principle and a technical effect thereof aresimilar and are not described herein again.

FIG. 11 is a schematic structural diagram of Embodiment 4 of an eNBaccording to the present invention. As shown in FIG. 11, the eNBprovided in this embodiment may include: a receiver 51, a processor 52,and a transmitter 53.

The receiver 51 is configured to receive a handover request sent by asource eNB eNB, where the handover request includes a context of acurrent serving small node, a context of user equipment UE, and anoffloading indication.

The processor 52 is configured to: determine, according to the handoverrequest, whether the UE can be handed over, whether the current servingsmall node can serve as a user plane serving node after the UE is handedover, and whether the target eNB can serve as a control plane servingnode after the UE is handed over, and if the UE can be handed over, thecurrent serving small node can serve as the user plane serving nodeafter the UE is handed over, and the target eNB can serve as the controlplane serving node after the UE is handed over, generate RRCreconfiguration information of the UE and offloading configurationinformation of the current serving small node.

The transmitter 53 is configured to send, to the source eNB, a handoverrequest acknowledgment that carries the RRC reconfiguration informationof the UE and the offloading configuration information of the currentserving small node, so that the source eNB sends the RRC reconfigurationinformation of the UE to the UE, and sends the offloading configurationinformation of the current serving small node to the current servingsmall node.

Further, the foregoing receiver 51 is further configured to receive anuplink synchronization message by the UE after the UE completesoffloading configuration according to the RRC reconfigurationinformation of the UE; the transmitter 53 is further configured todeliver a timing advance TA and an uplink grant to the UE; the foregoingreceiver 51 is further configured to receive an offloading configurationsuccess message sent by the UE based on the TA and the uplink grant.

Further, the foregoing transmitter 53 is further configured to send a UEoffloading configuration success indication to the current serving smallnode, so that the current serving small node confirms that the UEcompletes the offloading configuration.

The eNB in this embodiment may be configured to execute a technicalsolution in the foregoing method embodiment shown in FIG. 3 or FIG. 4,and an implementation principle and a technical effect thereof aresimilar and are not described herein again.

FIG. 12 is a schematic structural diagram of Embodiment 2 of a smallnode according to the present invention. As shown in FIG. 12, the smallnode provided in this embodiment may include: a receiver 61, a processor62, and a transmitter 63.

The receiver 61 is configured to receive offloading configurationinformation sent by a source eNB eNB, where the offloading configurationinformation is sent after the source eNB receives a handover requestacknowledgment sent by a target eNB to which user equipment UE is to behanded over, and the offloading configuration information includesconfiguration information required for establishing a bearer with thetarget eNB and configuration information required for establishing auser plane connection to the UE.

The processor 62 is configured to: perform offloading configurationaccording to the offloading configuration information, buffer user planedata of the UE, and record a sending status of the user plane data ofthe UE.

The transmitter 63 is configured to: after it is confirmed that the UEcompletes the offloading configuration, send, according to configurationinformation obtained after offloading configuration of the small nodeand the sending status of the user plane data of the UE, the user planedata of the UE buffered by the processor 62.

Optionally, the receiver 61 is further configured to receive a UEoffloading configuration success indication sent by the target eNB;correspondingly, the processor 62 is further configured to confirm,according to the UE offloading configuration success indication, thatthe UE completes the offloading configuration.

Optionally, the receiver 61 is further configured to receive an uplinksynchronization message sent by the UE, and the transmitter 63 isfurther configured to deliver a timing advance TA and an uplink grant tothe UE.

The receiver 61 is further configured to receive an offloadingconfiguration success message sent by the UE based on the TA and theuplink grant.

Correspondingly, the processor 62 is further configured to confirm,according to the offloading configuration success message, that the UEcompletes the offloading configuration.

Further, the user plane data of the UE buffered by the processor 62includes buffered uplink user plane data and buffered downlink userplane data.

The transmitter 63 is specifically configured to: after it is confirmedthat the UE completes the offloading configuration, according to theconfiguration information obtained after the offloading configuration ofthe small node and the sending status that is of the user plane data ofthe UE and is recorded by the processor 62, send, to the UE, thedownlink user plane data buffered by the processor 62, and send, to thetarget eNB, the uplink user plane data buffered by the processor 62.

Further, the downlink user plane data buffered by the processor 62includes downlink user plane data from the source eNB and downlink userplane data from the target eNB.

The transmitter 63 is specifically configured to: after it is confirmedthat the UE completes the offloading configuration, send, to the UE, thedownlink user plane data from the source eNB according to theconfiguration information obtained after the offloading configuration ofthe small node and the sending status that is of the user plane data ofthe UE and is recorded by the processor 62; and after sending thedownlink user plane data from the source eNB is completed, send, to theUE, the downlink user plane data from the target eNB according to theconfiguration information obtained after the offloading configuration ofthe small node and the sending status that is of the user plane data ofthe UE and is recorded by the processor 62.

The small node in this embodiment may be configured to execute atechnical solution in the foregoing method embodiment shown in FIG. 5,and an implementation principle and a technical effect thereof aresimilar and are not described herein again.

A person of ordinary skill in the art may understand that all or some ofthe steps of the method embodiments may be implemented by a programinstructing relevant hardware. The program may be stored in acomputer-readable storage medium. When the program runs, the steps ofthe method embodiments are performed. The foregoing storage mediumincludes: any medium that can store program code, such as a ROM, a RAM,a magnetic disk, or an optical disc.

Finally, it should be noted that the foregoing embodiments are merelyintended for describing the technical solutions of the presentinvention, but not for limiting the present invention. Although thepresent invention is described in detail with reference to the foregoingembodiments, a person of ordinary skill in the art should understandthat they may still make modifications to the technical solutionsdescribed in the foregoing embodiments or make equivalent replacementsto some or all technical features thereof, without departing from thescope of the technical solutions of the embodiments of the presentinvention.

What is claimed is:
 1. A method, comprising: sending, by a source basestation, a handover request to a target base station, wherein thehandover request comprises an identity of a current serving node and aninformation element that is used to uniquely define, on an interfacebetween the current serving node and the source base station, a serialnumber of a user equipment (UE), wherein the current serving node is anaccess node of a cell; receiving, by the source base station, a handoverrequest acknowledgment from the target base station, wherein thehandover request acknowledgment comprises radio resource control (RRC)reconfiguration information of the UE and configuration information ofthe current serving node; sending, by the source base station, theconfiguration information of the current serving node to the currentserving node to maintain transmission of user plane data in the currentserving node, and sending the RRC reconfiguration information of the UEto the UE; and receiving, by the source base station, a context releaserequest from the target base station.
 2. The method according to claim1, after the receiving a context release request from the target basestation, comprising: sending, by the source base station, a resourcerelease request to the current serving node for releasing a resourcethat is established with the source base station and that is related tothe UE.
 3. An apparatus, comprising: a memory storing programinstructions; and a processor coupled to the memory; wherein whenexecuted by the processor, the instructions cause the apparatus to: senda handover request to a target base station, wherein the handoverrequest comprises an identity of a current serving node and aninformation element that is used to uniquely define, on an interfacebetween the current serving node and a source base station, a serialnumber of a user equipment (UE), wherein the current serving node is anaccess node of a cell; receive a handover request acknowledgment fromthe target base station, wherein the handover request acknowledgmentcomprises radio resource control (RRC) reconfiguration information ofthe UE and configuration information of the current serving node; sendthe configuration information of the current serving node to the currentserving node to maintain transmission of user plane data in the currentserving node, and send the RRC reconfiguration information of the UE tothe UE; and receive a context release request from the target basestation.
 4. The apparatus according to claim 3, wherein the instructionsfurther cause the apparatus to: send a resource release request to thecurrent serving node for releasing a resource that is established withthe source base station and that is related to the UE.
 5. The methodaccording to claim 1, further comprising: in response to the receivingof the handover request, generating, by the target base station, the RRCreconfiguration information of the UE and the configuration informationof the current serving node; and sending, by the target base station,the handover request acknowledgment to the source base station.
 6. Themethod according to claim 5, further comprising: receiving, by thetarget base station, a configuration success message from the UE; andsending, by the target base station, a configuration success indicationto the current serving node to inform that the UE completesconfiguration.
 7. The method according to claim 1, further comprising:performing configuration based on the configuration information of thecurrent serving node, by the current serving node, to maintaintransmission of user plane data in the current serving node after the UEis handed over from the source base station to the target base station.8. The method according to claim 7, further comprising: receiving, bythe current serving node, a configuration success indication from thetarget base station, wherein the configuration success indication isused to inform that the UE completes configuration.
 9. The methodaccording to claim 7, further comprising: receiving, by the currentserving node, a resource release request from the source base station;and releasing, by the current serving node, a resource that wasestablished with the source base station and that is related to the UE.10. A communications system comprising a source base station, a targetbase station and a serving node, wherein the source base station isconfigured to send a handover request to the target base station,wherein the handover request comprises an identity of the serving nodeand an information element that is used to uniquely define, on aninterface between the serving node and the source base station, a serialnumber of a user equipment (UE), wherein the serving node is an accessnode of a cell; the target base station is configured to in response tothe receiving of the handover request, generate a radio resource control(RRC) reconfiguration information of the UE and configurationinformation of the serving node, and send a handover requestacknowledgment to the source base station, wherein the handover requestacknowledgment comprises the RRC reconfiguration information of the UEand the configuration information of the serving node; the source basestation is further configured to send the configuration information ofthe serving node to the serving node, and send the RRC reconfigurationinformation of the UE to the UE; the serving node is configured toperform configuration based on the configuration information of theserving node to maintain transmission of user plane data in the servingnode after the UE is handed over from the source base station to thetarget base station; and the target base station is further configuredto send a context release request to the source base station.
 11. Thesystem according to claim 10, wherein the target base station is furtherconfigured to receive a configuration success message from the UE, andsend a configuration success indication to the serving node to informthat the UE completes configuration.
 12. The system according to claim10, wherein the source base station is further configured to send aresource release request to the serving node; and the serving node isfurther configured to, in response to the resource release request,release a resource that was established with the source base station andthat is related to the UE.
 13. A non-transitory computer-readablestorage medium comprising instructions which, when executed by acomputer hardware of network device, cause the network device to: send ahandover request to a target base station, wherein the handover requestcomprises an identity of a current serving node and an informationelement that is used to uniquely define, on an interface between thecurrent serving node and a source base station, a serial number of auser equipment (UE), wherein the current serving node is an access nodeof a cell; receive a handover request acknowledgment from the targetbase station, wherein the handover request acknowledgment comprisesradio resource control (RRC) reconfiguration information of the UE andconfiguration information of the current serving node; send theconfiguration information of the current serving node to the currentserving node to maintain transmission of user plane data in the currentserving node, and send the RRC reconfiguration information of the UE tothe UE; and receive a context release request from the target basestation.
 14. The non-transitory computer-readable storage mediumaccording to claim 13, wherein the instructions, when executed by thecomputer hardware, further cause the network device to: send a resourcerelease request to the current serving node for releasing a resourcethat is established with the source base station and that is related tothe UE.